Activity coefficients of individual ions in LaCl₃ from the II+IW theory^*

^*This paper is dedicated to honour of the lifetime achievement of Johann Fischer in the field of statistical mechanics of condensed phases.

ABSTRACT

We investigate the individual activity coefficients of ions in LaCl₃ using our theory that is based on the competition of ion–ion (II) and ion–water (IW) interactions. The II term is computed from Grand Canonical Monte Carlo simulations on the basis of the implicit solvent model of electrolytes using hard sphere ions with Pauling radii. The IW term is computed on the basis of Born's treatment of solvation using experimental hydration-free energies. The results show good agreement with experimental data for La³⁺. This agreement is remarkable considering the facts that (i) the result is the balance of two terms that are large in absolute value (up to 20 kT) but opposite in sign, and (ii) that our model does not contain any adjustable parameter. All the parameters used in the model are taken from experiments: concentration-dependent dielectric constant, hydration free energies and Pauling radii.

KEYWORDS:

• Electrolytes
• activity coefficient
• Monte Carlo
• solvation

Acknowledgments

We gratefully acknowledge the financial support of the Hungarian National Research Fund (OTKA NN113527) in the framework of ERA Chemistry.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Hungarian National Research Fund [Grant Number OTKA NN113527].